1. Field of the Invention
This invention relates to a method for forming an electrode for a fuel cell. More particularly, this invention relates to a method for forming an electrode for a fuel cell wherein the method uses a resole resin binder that serves to increase the operating life of the electrode.
2. Description of the Related Art
One power generation system that has attracted widespread recent interest in the automotive industry is the low temperature fuel cell. One type of low temperature fuel cell is the polymer electrolyte membrane fuel cell which comprises a polymeric electrolyte membrane sandwiched between two electrodes, i.e., an anode and a cathode. The fuel cell generates electrical power by bringing a fuel into contact with the anode and an oxidant into contact with the cathode. The fuel is typically a hydrogen-containing material (for example, water, methane, methanol or pure hydrogen), and may be supplied to the fuel cell in liquid form or gaseous form, such as hydrogen gas. The fuel is introduced at the anode where the fuel reacts electrochemically in the presence of a catalyst on the anode to produce electrons and protons in the anode. The electrons are circulated from the anode to the cathode through an electrical circuit connecting the anode and the cathode. Protons pass through the electrolyte membrane (which is an electron insulator and keeps the fuel and the oxidant separate) to the cathode. Simultaneously, an oxygen-containing oxidant, such as oxygen gas or air, is introduced to the cathode where the oxidant reacts electrochemically in the presence of a catalyst on the cathode consuming the electrons circulated through the electrical circuit and the protons at the cathode. The halfcell reactions at the anode and the cathode are, respectively: H2→2H++2e− and ½O2+2H++2e−→H2O. The external electrical circuit withdraws electrical current and thus receives electrical power from the cell. The overall fuel cell reaction produces electrical energy which is the sum of the separate halfcell reactions written above.
Various processes are known for forming the fuel cell electrodes. For example, U.S. Pat. No. 4,506,028 discloses a process in which a mixture of carbon fibers, a resin binder such as a powdery phenol resin, and a granular pore regulator are press-molded and cured to form an electrode. U.S. Pat. Nos. 4,666,755 and 4,687,607 disclose processes in which a mixture of carbon fibers, a resin binder such as a phenol resin, and a granular pore regulator are press-molded over a support web and cured to form an electrode. U.S. Pat. No. 4,814,307 discloses a process in which a dry blend of carbon fibers, a phenol resin binder, and a granular pore regulator are extruded, press-molded and cured to form an electrode.
While the aforementioned processes for forming the fuel cell electrodes may be satisfactory, they do have certain disadvantages. For instance, these processes may use materials that produce a fuel cell electrode having less than optimal operating efficiency and life. Therefore, there is a need for a method for forming fuel cell electrodes wherein the method does not use materials that limit electrode operating efficiency or operating life.